This study looks at treatments for people at risk for a specific type of early Alzheimer's disease (AD) caused by a genetic mutation. **Alzheimer's disease** is a brain disorder that slowly destroys memory and thinking skills. The study has two stages:

**Stage 1:** Tests if the study drug can stop or slow down the build-up of a harmful protein called *amyloid beta (Aβ)* in the brain. This is done using a special brain scan called **PET imaging**.

**Stage 2:** Looks at how reducing Aβ affects other signs of Alzheimer's disease by comparing results with those from a group who didn't receive the drug.

• The study lasts for about 8 years: 4 years for Stage 1 and another 4 for Stage 2.
• Participants are people with a family history of Alzheimer's mutations, but who currently show no symptoms.
• Participants will need to attend regular clinic visits and will be monitored through various tests, including brain scans and blood tests.